Noise measurement apparatus and test apparatus

Abstract

Provided is a noise measurement apparatus that measures noise at a location under measurement, comprising a self-excited oscillator that is provided at the location under measurement and that outputs an oscillation signal in which is sequentially accumulated, in each cycle, the noise at the location under measurement; a transmission path that transmits the oscillation signal output by the self-excited oscillator; and a measuring unit that measures noise added to the oscillation signal transmitted through the transmission path. The measuring unit may measure the noise at the location under measurement by differentiating noise added to the oscillation signal transmitted through the transmission path.

1. A noise measurement apparatus comprising:
 a self-excited oscillator that is provided at a location under measurement in a circuit substrate, semiconductor chip, or wafer and that outputs an oscillation signal in which is sequentially accumulated, in each oscillation period, a first noise occurring at the location under measurement; 
 a transmission path that transmits the oscillation signal output by the self-excited oscillator and adds a second noise to the oscillation signal; and 
 a measuring unit that receives the oscillation signal including the sequentially accumulated first noises and the second noise, and calculates the first noise occurring at the location under measurement based on a difference between the received oscillation signal and a delayed signal obtained by delaying the received oscillation signal by a delay amount that is an integer multiple of an average period of the oscillation period. 
 
     
     
       2. The noise measurement apparatus according to  claim 1 , wherein the measuring unit includes:
 a delay circuit that receives the oscillation signal transmitted through the transmission path, after the oscillation signal is branched, and outputs a delayed signal obtained by delaying the received oscillation signal by a prescribed delay amount; 
 a phase comparator that detects a phase difference between the oscillation signal transmitted by the transmission path and the delayed signal output by the delay circuit; and 
 a noise calculating section that calculates the first noise based on the phase difference detected by the phase comparator. 
 
     
     
       3. The noise measurement apparatus according to  claim 2 , wherein the noise calculating section includes:
 a spectrum calculating section that calculates a frequency spectrum of the first noise, based on the phase difference detected by the phase comparator for each cycle of the oscillation signal; 
 an extracting section that extracts, from the frequency spectrum, a frequency component that is less than a predetermined frequency; and 
 a calculating section that calculates the first noise based on the component of the frequency spectrum extracted by the extracting section. 
 
     
     
       4. A noise measurement apparatus that measures noise distribution in a circuit substrate, comprising:
 a plurality of self-excited oscillators that are each provided at a different location under measurement in the circuit substrate, and that each output an oscillation signal in which is sequentially accumulated, in each oscillation period, a first noise occurring at the location under measurement; 
 a transmission path that transmits the oscillation signal output by each self-excited oscillator and adds a second noise to each oscillation signal; 
 a measuring unit that, for each oscillation signal, second noise receives the oscillation signal including the sequentially accumulated first noises and the second noise, and calculates the first noise occurring at the location under measurement based on a difference between the received oscillation signal and a delayed signal obtained by delaying the received oscillation signal by a delay amount that is an integer multiple of an average period of the oscillation period; and 
 a distribution calculating section that calculates the noise distribution in the circuit substrate based on the first noise in each oscillation signal calculated by the measuring unit. 
 
     
     
       5. The noise measurement apparatus according to  claim 4 , wherein the transmission path includes a plurality of individual wirings that are provided to correspond one-to-one with the plurality of self-excited oscillators and that each transmit the oscillation signal output by the corresponding self-excited oscillator, and the noise measurement apparatus further comprises a selecting section that receives the oscillation signals transmitted through each of the plurality of individual wirings, sequentially selects the oscillation signals, and inputs the sequentially selected oscillation signals to the measuring unit. 
     
     
       6. The noise measurement apparatus according to  claim 4 , wherein the transmission path includes:
 a serial wiring that connects the plurality of self-excited oscillators in series with the measuring unit; and 
 a plurality of individual switching sections that are provided to correspond one-to-one with the plurality of self-excited oscillators, and that each receive output of the self-excited oscillator at a previous stage and output of the corresponding self-excited oscillator, and switch which of the outputs is passed as output of the present stage, and the noise measurement apparatus further includes a selecting section that (i) sequentially selects one of the individual switching sections, (ii) causes the selected individual switching section to pass the output of the corresponding self-excited oscillator and causes the other individual switching sections to pass the output of the self-excited oscillator at the previous stage, thereby sequentially selecting each of the oscillation signals output by the self-excited oscillators, and (iii) inputs the selected oscillation signals to the measuring unit. 
 
     
     
       7. The noise measurement apparatus according to  claim 5 , wherein the measuring unit includes:
 a delay circuit that receives the oscillation signal input from the selecting section, after the oscillation signal is branched, and outputs a delayed signal obtained by delaying the received oscillation signal by a prescribed delay amount; 
 a phase comparator that detects a phase difference between the oscillation signal input from the selecting section and the delayed signal output by the delay circuit; and 
 a noise calculating section that calculates the first noise at the location under measurement selected by the selecting section, based on the phase difference detected by the phase comparator. 
 
     
     
       8. The noise measurement apparatus according to  claim 7 , wherein the measuring unit further includes an adjusting section that adjusts the delay amount of the delay circuit based on the phase difference output by the phase comparator, such that a DC component of the phase difference output by the phase comparator becomes substantially zero. 
     
     
       9. The noise measurement apparatus according to  claim 7 , wherein the noise calculating section includes:
 a spectrum calculating section that calculates a frequency spectrum of the first noise, based on the phase difference detected by the phase comparator for each cycle of the oscillation signal; 
 an extracting section that extracts, from the frequency spectrum, a frequency component that is less than a predetermined frequency; and 
 a calculating section that calculates the first noise based on the component of the frequency spectrum extracted by the extracting section. 
 
     
     
       10. The noise measurement apparatus according to  claim 5 , further comprising a circuit control section that stops oscillation performed by self-excited oscillators other than the self-excited oscillator that is selected by the selecting section. 
     
     
       11. The noise measurement apparatus according to  claim 4 , wherein the circuit substrate includes a plurality of operation circuits, and each self-excited oscillator is provided at a location under measurement according to a corresponding operation circuit. 
     
     
       12. The noise measurement apparatus according to  claim 11 , wherein the circuit substrate further includes a power supply section that supplies the operation circuits with supply power, and the noise measurement apparatus further comprises a circuit control section that, when a 1/f noise component that is inversely proportional to frequency is among the first noise, causes the measuring unit to measure the combined first and second noise after stopping the power supply section and the operation circuits. 
     
     
       13. The noise measurement apparatus according to  claim 11 , wherein the circuit substrate further includes a power supply section that supplies the operation circuits with supply power, and the noise measurement apparatus further comprises a circuit control section that, when a noise component that is not dependent on frequency is among the first noise, causes the measuring unit to measure the combined first and second noise after causing the power supply section and the operation circuits to operate. 
     
     
       14. A noise measurement apparatus, comprising:
 a transmission path that i) transmits an oscillation signal output by a self-excited oscillator provided at a location under measurement in the device under test, a first noise occurring at the location under measurement being sequentially accumulated in the oscillation signal in each oscillation period, and ii) adds a second noise to the oscillation signal; and 
 a measuring unit that receives the oscillation signal including the sequentially accumulated first noises and the second noise, and calculates the first noise occurring at the location under measurement based on a difference between the received oscillation signal and a delayed signal obtained by delaying the received oscillation signal by a delay amount that is an integer multiple of an average period of the oscillation period.